WASHINGTON -- Sarah Palin faces a huge problem in tonight's vice presidential debate: She's in danger of becoming a national punch line.
As a result, the Republican's 90-minute debate with Democratic rival Joe Biden could be her last big chance to convince voters that she's got what it takes to run the country.
"She has a lot to prove," said James Riddlesperger, a professor of political science at Texas Christian University, "and this is a real opportunity for her to do so."
Biden also faces some risks.
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"He's like the champion getting into the ring with Rocky Balboa. He can't appear to be a bully," said vice presidential scholar Timothy Walch. The longtime Delaware senator also has a history of putting his foot in his mouth, and a gaffe while debating Palin could cost him.
The debate, though, is largely about Palin, the Alaska governor who was barely known in the Lower 48 until John McCain put her on the ticket just before last month's Republican National Convention.
She was an instant hit, at least with Republicans, charming the GOP convention with her plain-spoken, frontier woman ways and her solid conservative credentials.
Since then, however, the nation has seen another Palin: carefully managed, kept under wraps, often scripted and seemingly out of her depth. A poll released Wednesday by the Pew Research Center reported, "opinions about Sarah Palin have become increasingly negative." The Sept. 27-29 survey found that 51 percent of the public think she's not qualified to be vice president, and 37 percent think she is qualified. Just after the GOP convention, some 52 percent thought she was ready.
Worse, Palin has become the butt of late night jokes.
On "Saturday Night Live," comedian Tina Fey's dead-on impression of Palin has parodied her as a rambling, perky celebrity unfamiliar with the day's biggest issues.
Experts say Palin has done too little to overcome that image. Her interviews last week with CBS' Katie Couric have been widely ridiculed.
Conservative columnist Kathleen Parker led the charge. Palin's TV interviews, she wrote, "revealed an attractive, earnest, confident candidate. Who is Clearly Out of Her League." Parker urged Palin to leave the ticket, imploring: "Do it for your country."
Biden, a U.S. senator since 1973, knows that he has to be careful to avoid looking like a Washington know-it-all.
"It could be very difficult for him to escape looking condescending," Riddlesperger said.
Biden also is gaffe-prone. Last week he told CBS: "When the stock market crashed, Franklin D. Roosevelt got on the television and didn't just talk about the, you know, the princes of greed. He said, 'Look, here's what happened.' "
The stock market crashed in 1929 and Roosevelt didn't become president until 1933. And when FDR spoke to the nation, it was on radio because television wasn't available.